基于点云的植株表型构建和反射率方向性分析

三维激光扫描可瞬时高效地采集点云信息,在获取植物表型特征上具有独特的优势。植株不规则的几何结构导致了其复杂的光辐射过程。本文使用激光扫描仪采集了四种代表性植株的稠密点云,数字化为三维模型以准确计算结构表型参数。通过将激光点云计算的准确的叶倾角分布和叶面积指数替代传统的SAIL模型中的经验参数,减少了其中间参数,提高了模拟精度。并对模拟反射率和实测反射率进行多角度分析,发现模拟结果在主平面方向有较大提高,垂直主平面方向提高程度相对较弱；植被光谱吸收谷,如450 nm、670 nm,具有较强的光谱异性的同时,结构参数的影响也较为突出,改进后的效果明显,而在近红外反射峰如860 nm则无明显改进。通过本文的研究,证明了利用激光快速获取植物表型参数的可行性,并成功利用准确结构参数解决辐射传输中的难点问题。

Plant phenotype construction and reflectance orientation analysis based on point clouds data

Three-dimensional laser scanning can collect point cloud information instantaneously and efficiently,and has unique advantages in obtaining plant phenotypic characteristics. The irregular geometric structure of the plant leads to its complex light radiation process. In this paper,dense spots of four representative plants were collected by laser scanner,and digitized as three-dimensional model to calculate structural phenotypic parameters accurately. By replacing the traditional empirical parameters of the SAIL model with the accurate leaf inclination angle distribution and leaf area index calculated by the laser point cloud,the intermediate parameters are reduced and the simulation accuracy is improved. And multi angle analysis,the simulated reflectance and measured reflectivity showed that simulation results have greatly improved in the direction of the main plane,vertical plane direction to improve the degree of vegetation is relatively weak;absorption valley,such as 450 nm,670 nm,has a strong anisotropic spectrum at the same time,the influence of structure parameters is also more prominent. The effect of improvement is obvious,while in the near infrared reflectance peaks such as 860 nm,it has no obvious improvement. In this paper,the feasibility of obtaining the plant phenotypic parameters by laser is proved,and the accurate structure parameters are successfully used to solve the difficult problems in the radiation transfer.